The present invention claims a priority based on Japanese Patent Application No. H10-214486, the content of which is incorporated hereinto by reference in its entirety.
1. Field of the Invention
This invention relates to a digital camera, a camera main body in a digital camera system and a method for processing a signal.
2. Description of the Related Art
There is a conventional digital camera which comprises an image sensing unit including a taking lens and an image pick-up element which converts an object image focused by the taking lens into an image signal and a camera main body including an image processing portion by which the image signal is subjected to a prescribed image processing.
As the aforementioned image pick-up element, a CCD (charged coupled device) as a photoelectric conversion element is generally used. When the optical image of the object is focused onto the surface of the CCD by the taking lens, the object image is photoelectrically converted into an analog image signal by the CCD. The generated analog image signal is converted into a digital image signal, and then the digital image signal is subjected to a predetermined image processing. Thus, image data can be obtained.
In a conventional digital camera of this kind, it is known that the image sensing unit including the taking lens, the image pick-up element and an analog circuit for the image pick-up element, is detachably connected to the camera main body and that the image sensing unit can be electrically connected to the camera main body by way of a cable in a case that the image sensing unit is detached from the camera main body. For example, the Japanese Patent Laid-open Publication No. H10-79874 discloses that the image sensing unit is detachably connected to the camera main body and that the phase delay of the image signal occurred in a case where the image sensing unit is connected to the camera main body via the cable is corrected.
In the aforementioned conventional digital camera, the A/D converter which converts the analog image signal generated by the CCD into the digital image signal is provided in the camera main body and the analog image signal outputted from the image sensing unit is transmitted to the camera main body as it is via the cable so as to be subjected to the A/D conversion at the camera main body. As a result, the image signal may be influenced by noise when the image signal is transmitted to the camera main body. Thus, the practical length of the cable will be limited to about 1 meter.
In the meantime, in order to transmit the analog signal through a cable of long length, it may be considered to raise the gain when amplifying the analog image signal in the image sensing unit. However, in this case, there will be the drawback that noise will be increased at the image sensing unit side and the power consumption rate of the batteries as a power source will be increased.
Therefore, it is an object of the present invention to provide a digital camera for practical use which can obtain an appropriate image signal without being influenced by noise even in a case where an image sensing unit is connected to a camera main body via a cable and is low in energy consumption rate.
Another object of the present invention is to provide a camera main body suitable for use in a digital camera system in which an image sensing unit and the camera main body are connected via a cable.
Still another object of the present invention is to provide a method for processing a signal which is applicable to the aforementioned digital camera system.
According to one aspect of the present invention, a digital camera includes a camera main body, an image sensing unit which is detachably connected to the camera main body and electrically connectable to the camera main body via a cable in a state that the image sensing unit is detached from the camera main body. The image sensing unit includes a taking lens, an image pick-up element for picking up an object image focused by the taking lens, and an A/D converter which converts an analog image signal outputted from the image pick-up element into a digital image signal. The camera main body includes an image processing apparatus for subjecting the digital image signal outputted from the A/D converter to a prescribed image processing.
With this digital camera, since the image sensing unit including the taking lens and the image pick-up element is detachably connected to the camera main body and they are connectable with each other via the cable in a detached state, a photographing can be performed at any desired angles. In addition, since the A/D converter is provided in the image sensing unit, the converted digital image signal is transmitted to the camera main body. However, since the digital signal is not easily affected by noise, an appropriate image signal can be obtained at the camera main body side even if the image sensing unit is connected to the camera main body via the cable.